Data Engineer Professional cheat sheet
Last-minute reference for the Databricks Data Engineer Professional exam. This one tests production judgement, so most answers concern what survives contact with reality.
Exam facts
| Questions | 59 scored |
| Duration | 120 minutes |
| Fee | 200 USD |
| Validity | 2 years |
| Passing score | Not published by Databricks |
Section weights
| Section | Weight |
|---|---|
| Developing code for data processing | 22% |
| Cost & performance optimisation | 13% |
| Transformation, cleansing, quality | 10% |
| Monitoring and alerting | 10% |
| Security and compliance | 10% |
| Debugging and deploying | 10% |
| Data ingestion & acquisition | 7% |
| Data governance | 7% |
Production patterns
| Requirement | Answer |
|---|---|
| Exactly-once effect across restarts | Checkpointed offsets + idempotent or transactional sink |
| Python UDF dominating runtime on 400M rows | Built-in expressions or a vectorised UDF |
| Heavy spill joining 4 TB to 30 MB | Check why the small side is not broadcast |
| Identical behaviour for backfill and stream | One transformation, parameterised by read/write mode |
| Logic must be testable outside a notebook | Versioned module with unit tests |
| Cost tripled, data grew 20%, heavy listing | Small file accumulation → compact |
| Frequent filters on two high-cardinality columns | Cluster or z-order, not partition |
| Streaming job silently behind at peak | Input backlog / source lag |
| Alert only when actionable | Alert on final failure after retries |
Security and governance
- Erasure request on an append-only table → retained versions and downstream copies must be addressed within the retention policy. Deleting the current row is not enough.
- Service principal with workspace admin → excessive privilege; scope to what the job needs.
- Impact of a schema change → lineage in the governance catalog, not a code search.
- Divergent metric definitions → one certified, owned definition both tables converge on.
Ingestion
- CDC feed → ordered merge including deletes and late or out-of-order events
- Rate-limited API with partial pages → backoff, resumable pagination, completeness validation
The published-score trap
No passing score is published. At professional level the margin is narrower, so calibrate on a weighted practice test.
Night-before checklist
- Eight sections; code development is 22%
- Exactly-once = checkpoint + idempotent sink
- Cluster/z-order versus partition for high cardinality
- Check ID and proctoring rules — see exam day
Take the 20-question practice test.